Solid Energy is looking at putting out an underground coal fire that has burned north of Westport for more than 80 years.
The fire in the Lonely Fan part of the Millerton Mine started by spontaneous combustion in 1926 and has burned ever since.
State-owned Solid Energy needs to put the fire out before it can gain access to millions of tonnes of coal in the area, which it hopes to opencast mine.
It was difficult to say how big the fire was, or how deep, as it was situated in rolling topography, said spokesman Bryn Somerville.
The fire could burn with a fierce heat or sometimes just smoulder away, he said.
There was no shortage of fuel or air to the fire as the ground was fractured in many places. Engineers would try to take the heat out of the fire, he said.
Trials would start in the next few months once a continuous supply of water was in place.
Smoke from the fire is occasionally visible when it burns close to the surface. Underground coal fires are not uncommon and another underground fire is burning at the Strongman 2 Mine near Greymouth.
Meanwhile, Solid Energy showcased its efforts to improve water quality on the Stockton Plateau over the weekend.
Visitors were shown new water treatment systems, which Solid Energy has spent more than $45 million on over the last four years, the Westport News reported.
